Chemical process

ABSTRACT

This invention relates to the preparation of alkali metal hydrides and of alkali metal aluminum dihydrocarbon dihydrides and in particular to such compounds of sodium, potassium or lithium having in the case of the dihydrocarbon compounds hydrocarbon radicals containing from 2 to about 30 carbon atoms per radical. Such dihydrocarbon materials, as typified by sodium aluminum diethyl dihydride, and by the potassium or lithium counterparts, either singly or in mixtures with respect to alkali metals and/or hydrocarbon groups, are soluble and useful in inert aromatic hydrocarbon solutions and have excellent mild reducing properties for various functional groups such as carbonyl groups in various organic compounds. The alkali metal hydrides are useful in many known ways such as in condensation and alkylation reactions and as chemical intermediates such as in the preparation of the alkali metal aluminum dihydrocarbon dihydrides.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of application Ser. No. 512,120, filed Oct. 4, 1974.

DESCRIPTION OF THE PRIOR ART Alkali Metal Hydride Processes

One known method of preparing alkali metal hydrides utilizes the reaction of alkali metal and hydrogen in the presence of alkali metal hydride. In such operation, the alkali metal hydride may expedite the reaction but the effect is not truly catalytic being more a matter of surface effect since other particulate solid dispersants such as sand, clay, or the like, are about as effective. Even in such systems, it is considered desirable to operate with close control of the balance between alkali metal and hydrogen fed to prevent the existence of a liquid phase which may stop the reaction and cause rapid build-up of scale. Another factor involved in the use of alkali metal hydride as a dispersant is the problem of residual moisture in the reactants fed and in the reactor in start-up and the need to avoid water presence of the violent reaction with moisture characteristic of alkali metals and their hydrides.

In another method, alkali metal hydrides are prepared by reacting alkali metal and hydrogen in a heavy hydrocarbon oil diluent. Such processing usually provides a slurry type product that is no more than about 50 percent alkali metal hydride. It is difficult to remove the heavy hydrocarbon by vaporization or filtration which generally dictates the use of expensive solvent or extraction removal procedures or the shipment and use of the alkali metal hydride in the form of a dispersion in oil. Even these procedures have the disadvantage that the mineral oil diluent and extractant used must be water free.

Alkali Metal Aluminum Dihydrocarbon Dihydride Processes

Previously known processes for the preparation of alkali metal aluminum dihydrocarbon dihydrides have suffered from several disadvantages. German Pat. No. 918,928 describes the preparation of sodium or lithium aluminum dialkyl dihydrides by reacting dialkyl aluminum hydrides or dialkyl aluminum halides with sodium hydride or lithium hydride. These reactions preferably are conducted with oil-free alkali metal hydride to avoid the need for subsequent removal of the oil present with oil-dispersion alkali metal hydride.

The dialkyl aluminum halide reaction further suffers from the disadvantages that it requires the preparation of the halide material and that in the process some of the alkali metal value is converted to alkali metal halide salt of low value.

Another process for producing alkali metal aluminum dihydrocarbon dihydrides is shown in German Pat. 1,116,664 wherein trialkyl aluminum is reacted with alkali metal and hydrogen. This process suffers from the disadvantage that one of the three alkyl groups on the starting trialkyl aluminum is lost by conversion thereof to hydrocarbon.

Another process for producing alkali metal aluminum dihydrocarbon dihydrides is described in U.S. Pat. 3,686,248. Although this is an excellent process for producing the desired product in high yield, further improvement is desirable since at times there may be a tendency toward the deposition of aluminum on reactor surfaces.

SUMMARY OF THE INVENTION

The present process avoids much of the prior art difficulty associated with the preparation of alkali metal hydrides as well as with the preparation of alkali metal aluminum dihydrocarbon dihydrides. The present process provides a catalyzed process for producing alkali metal hydride at a high rate, in a high level of safety, and without contamination by heavy oil or other materials that are not desired in alkali metal aluminum dihydrocarbon dihydrides or other materials produced from the alkali metal hydrides.

Accordingly, the present invention relates to a process for producing alkali metal hydrides which comprises reacting alkali metal and hydrogen in the presence of a catalytic amount of at least about 0.001 percent by weight of alkali metal aluminum dihydrocarbon dihydride based on the alkali metal reactant fed to the process and in the presence of an inert solvent for the alkali metal aluminum dihydrocarbon dihydride. The reaction is performed under conditions suitable to form alkali metal hydride. As a result of performing the process, alkali metal hydride is produced which is useful in various ways. For example, it is highly desirable for the production of alkali metal aluminum dihydrocarbon dihydrides. Thus, the alkali metal hydride process is advantageously used in a novel process for producing alkali metal aluminum dihydrocarbon hydride.

In one aspect therefore, the present invention provides a process for producing alkali metal aluminum dihydrocarbon dihydrides which comprises reacting alkali metal and hydrogen in the presence of an inert aromatic hydrocarbon solvent for the alkali metal aluminum dihydrocarbon dihydride and a catalytic amount of at least about 0.001 percent by weight of alkali metal aluminum dihydrocarbon dihydride, under conditions suitable to form alkali metal hydride, thereby producing alkali metal hydride, and then reacting the alkali metal hydride with trihydrocarbon aluminum, aluminum and hydrogen, in the presence of said solvent under conditions suitable to form alkali metal aluminum dihydrocarbon dihydride thereby producing alkali metal aluminum dihydrocarbon dihydride.

In another aspect, the present invention provides a process for producing an alkali metal aluminum dihydrocarbon dihydride which comprises reacting alkali metal and hydrogen in the presence of an inert aromatic hydrocarbon solvent for the alkali metal aluminum dihydrocation dihydride and a catalytic amount of at least about 0.001 percent by weight of alkali metal aluminum dihydrocarbon dihydride based on the alkali metal fed to the process, and in the substantial absence of free aluminum, at a temperature of from about 100° to about 325° C; and a pressure of from about 50 to about 5000 psig for a period of time of from about 0.01 to about 12 hours, thereby producing alkali metal hydride, and then reacting the mixture of alkali metal hydride with aluminum, trihydrocarbon aluminum and hydrogen, in the presence of said solvent at a temperature of from about 100 to about 325° C and a pressure of from about 50 to about 5000 psig for a period of time of from about 0.01 to about 12 hours, thereby producing alkali metal aluminum dihydrocarbon dihydride.

In another aspect, the present invention provides a process for producing an alkali metal aluminum dihydrocarbon dihydride which comprises reacting alkali metal and hydrogen in the presence of aluminum and an inert aromatic hydrocarbon solvent for the alkali metal aluminum dihydrocarbon dihydride and a catalytic amount of at least about 0.001 percent by weight of alkali metal aluminum dihydrocarbon dihydride based on the alkali metal fed to the process, at a temperature of from about 180° to about 325° C; and a pressure of from about 50 to about 5000 psig for a period of time of from about 0.01 to about 12 hours, thereby producing alkali metal hydride, and then reacting the alkali metal hydride and the aluminum with trihydrocarbon aluminum and hydrogen, in the presence of said solvent at a temperature of from about 100° to about 325° C and a pressure of from about 50 to about 5000 psig for a period of time of from about 0.01 to about 12 hours, thereby producing alkali metal aluminum dihydrocarbon dihydride.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 of the drawings shows a group of three curves of pressure versus reaction time for the sodium hydride formation step of Examples I, II, and IV.

FIG. 2 of the drawings shows a group of two curves of pressure versus reaction time for the sodium hydride formation step of Examples V, VI and VII.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present process provides a way to avoid the foregoing and other problems of the prior art and at the same time provides a catalytic effect to enhance the rate of reaction of alkali metal and hydrogen in the formation of alkali metal hydride.

Preferably alkali metal used as reactant or in catalyst as well as that in product alkali metal hydride or product alkali metal aluminum dihydrocarbon dihydride is an alkali metal of Group I-A of the Periodic Table (Fischer Scientific Co., 1955), especially sodium, potassium or lithium, more preferably, sodium because of its excellent reactivity and availability at low cost.

The alkali metal M of the alkali metal aluminum dihydrocarbon dihydride (MAlR₂ H₂) used in the process as catalyst or produced in the process is preferably the same as the alkali metal reacted with hydrogen to produce the alkali metal hydride. This preference is directed toward securing a greater uniformity of product. In other instances, the alkali metal of the alkali metal aluminum dihydrocarbon dihydride is different from the alkali metal fed for the reaction with hydrogen. Thus, for example, one may use lithium, potassium, or sodium aluminum diethyl dihydride as catalyst in the preparation of sodium hydride or potassium hydride or lithium hydride. Mixtures of two or more alkali metals may be used as reactants or as catalyst components and the alkali metal reactants are suitably the same as the catalyst components or different therefrom.

Hydrocarbon groups in catalyst as well as in trihydrocarbon aluminum reactant R₃ Al where used in the processes of the present invention can be any suitable organic radicals or groups determined on a basis of reactivity, compatibility to the processing and desirability in the product, especially where alkali metal aluminum dihydrocarbon dihydride (MAIR₂ H₂) is a desired product. Since the R hydrocarbon groups in alkali metal aluminum dihydrocarbon dihydride are largely of a "carrier" nature, the Al--H bonds usually being the desired aspects, it is usually preferred to have the simplest practical R groups which in most instances are ethyl groups. In general, R of R₃ Al or NaAlR₂ H₂ is one or a mixture of two or more alkyl groups having from about 2 to about 30 carbon atoms per alkyl group. More preferably, R is similar or different alkyl group having from about 2 to about 6 carbon atoms per alkyl group. Preferably, the alkali metal aluminum dihydrocarbon dihydride is sodium aluminum diethyl dihydride or sodium aluminum diisobutyl hydride, especially the former. Thus, preferably the trihydrocarbon aluminum reactant R₃ Al used in the present process is triethyl aluminum or triisobutyl aluminum. Although the R groups are preferably essentially straight chain alkyl groups, where desired, other hydrocarbon groups, preferably other alkyl groups, including groups with olefinic unsaturation, branching, linkage to aluminum through secondary carbon atoms, etc., as well as groups with innocuous substitution may be used. In general, one does not desire to use groups containing adversely reactive constituents such as halogens and the like. Other typical preferred R groups are propyl, isopropyl, n-butyl, isobutyl, n-pentyl, n-hexyl, n-lauryl, and the like.

The amount of catalyst to be used in the catalyzed reaction of alkali metal and hydrogen to produce alkali metal hydride is not critical. In general, at least a catalytic amount is used. The minimum practical catalytic amount added as well as the optimum amount in toto is readily determined for specific cases by simple routine experimentation using the procedures described herein and used in the appended examples. In general, the minimum catalytic amount is about 0.001 percent by weight based upon the alkali metal fed for reaction with the hydrogen. On the other hand, since the present invention discloses the basic catalysis, the term "effective amount" includes any amount deliberately added or retained to achieve catalysis. Although there is no upper limit upon the amount of catalyst that can be used, generally there is no particular need to feed more catalyst than about 50 percent by weight based upon the alkali metal fed for the reaction and above this amount, reactor capacity is needlessly monopolized by catalyst. Of course, if one wishes to use more catalyst, the fundamental process is admirably suited to such in most instances since preferred catalysts are soluble in aromatic hydrocarbons such as toluene and others recited herein while the reactant sodium and product sodium hydride are virtually insoluble in such hydrocarbons. Thus simple decantation or filtration operations can readily separate the catalyst. Furthermore, since the most preferred catalysts are materials that are also especially desirable products readily manufactured as disclosed herein from alkali metal hydride, the separation of catalyst from the alkali metal hydride is frequently entirely unnecessary leaving the reactor monopolization factor as the principal reason for specifying an upper limit upon the amount of catalyst to use.

Accordingly, the preferred amount of catalyst is from about 0.1 percent to about 50 percent by weight based on the alkali metal fed to the process for the reaction with hydrogen, especially from about 1 percent to about 20 percent by weight, particularly from about 10 to about 15 percent by weight.

The solvents suitable for the present invention are quite limited. In the first place it is obvious that any solvent or diluent used must be inert, that is, not adversely reactive with any of the materials present or itself adversely degraded under the conditions used. Secondly, the solvent or diluent is desired to be a solvent for the catalyst used in the preparation of the alkali metal hydride or at least for the minimum effective amount of catalyst. The solvent or diluent is suitably merely a diluent in regard to the alkali metal reactant or alkali metal hydride product. In general, suitable solvents or diluents are readily identified from solubility data and reactivity properties so that candidates are readily revealed by routine experimentation following the appended examples.

Suitable solvents or diluents are inert aromatic hydrocarbon solvents including toluene, benzene, xylene, ethylbenzene.

As noted hereinbefore, the amount of solvent or diluent used is not critical. In general, one desires to use enough solvent to solubilize at least the minimum effective amount of catalyst. Usually, it is preferred to use enough solvent to maintain a fluid system which can be agitated effectively during the respective reactions by conventional propeller or turbine stirrers for both the production of alkali metal hydride and for the production of the alkali metal aluminum dihydrocarbon dihydride. Where the production of alkali metal hydride is for the purpose of converting it to alkali metal aluminum dihydrocarbon dihydride, it is usually preferred to feed at the step of production of the alkali metal hydride an amount of from about one-quarter to about 100 percent of the solvent required to solubilize all of the final product alkali metal aluminum dihydrocarbon dihydride. In this range, but especially with about one-half of the required solvent for the product alkali metal aluminum dihydrocarbon dihydride final product, one obtains a good compromise between fluidity of the reaction masses and avoidance of excessive monopolization of reactor volume by solvent. Where less than the total solvent required to solubilize the product alkali metal aluminum dihydrocarbon dihydride is fed during the reactions, it is usually desired to add the balance of the needed solvent to the reaction mass after the reaction to facilitate product removal from the reactor; however, such may not be desirable where a heel of the product alkali metal aluminum dihydrocarbon dihydride is retained in the reactor as catalyst for a subsequent run.

The preferred alkali metal aluminum dihydrocarbon dihydride products are soluble to at most to only about 30 percent by weight in the solvents. Normally this is not of any particular problem except where the production of the most concentrated product alkali metal aluminum dihydrocarbon dihydride is desired, for example, to minimize shipping costs. In such instances, the solubility of alkali metal aluminum dihydrocarbon dihydride can be enchanced considerably through the use of suitable innocuous Lewis bases as co-solvents as described in U.S. Pat. No. 3,696,047, the disclosure of which, like the disclosure of U.S. Pat. No. 3,686,248, is herewith incorporated herein by reference. Thus, for example, as shown by Example V, one can add such Lewis bases as tetrahydrofuran after the final step reaction. In general, it is preferred to avoid the presence of the Lewis bases during the hydriding reactions so that where a heel of the alkali metal aluminum dihydrocarbon dihydride is to be retained in the reactor or a portion withdrawn and returned as catalyst, it is preferred to add the Lewis base to the product system after provision has been made for the retention of catalyst material.

The reaction to produce alkali metal aluminum dihydrocarbon dihydride from alkali metal hydride requires the feed not only of trihydrocarbon aluminum and hydrogen but also the feed of aluminum, preferably of a reactive or activated type, preferably in the form of powder. Preferred aluminum powder contains an alloying agent such as titanium or zirconium to enhance the reactivity. It is believed that the reactions proceed as indicated hereinafter:

    3 NaH + 2 R.sub.3 Al → 2 NaAlR.sub.3 H + NaH

    2 naAlR.sub.3 H + NaH + Al + 11/2 H.sub.2 → 3 NaAlR.sub.2 H.sub.2

the addition of the extra aluminum to the NaH or to the combined NaH and R₃ Al system is not particularly convenient. Thus frequently it is preferred to add the required amount of aluminum to the reactor prior to the reaction which produces the alkali metal hydride and to carry it on through to the point where it reacts. The presence of the aluminum does not adversely affect the production of the alkali metal hydride when the temperature of the first step of the reaction is above about 180° C. Below this temperature, in the presence of free aluminum, the first step produces trialkali metal aluminum hexahydride. Thus where one wishes to operate the first step of the present process to produce alkali metal hydride at temperatures from about 100° C to about 180° C, one preferably does not add the free aluminum until after the formation of the alkali metal hydride is concluded. Alternatively where it is desired to feed the aluminum at the first stage and operate at from about 100° C to about 180° C, and also use a ratio of alkali metal to hydrogen at the first step equivalent to that in alkali metal hydride, one limits the amount of hydrogen accordingly and does not feed the extra hydrogen required for complete conversion of all alkali metal to the trialkali metal aluminum hexahydride at the first hydriding step. In any event, the amount of aluminum fed overall is usually at least the amount required for conversion of the alkali metal hydride and trihydrocarbon aluminum to alkali metal aluminum dihydrocarbon dihydride at the last stage. The feed of an excess of aluminum, e.g. from about stoichiometric to about 50 percent excess above stoichiometric, is usually desirable to insure complete reaction at a rapid rate. The feed of an excess of aluminum normally presents no problem since the excess left unreacted is readily retained in the reactor or separated and returned to it for use in a subsequent batch.

The temperature of the reactions is critical to some extent but in view of the present disclosure, one skilled in the art does not require undue experimentation in finding optimum conditions for any particular situation.

In general, the present process is suitably conducted at a temperature of from about 100° C to about 325° C. To achieve good reaction rates and avoid by-product formation and other high temperature problems, a narrower temperature range of from about 150° C to about 275° C is preferred, especially the range of from about 175° C to about 225° C. Several typical temperatures are 125° C, 150° C, 160° C, 175° C, 180° C, 200° C and 225° C.

As noted in the foregoing, there is an important consideration of the present process in regard to temperature. At temperatures below about 180° C, the reaction of alkali metal and hydrogen forms trialkali metal aluminum hexahydride rather than alkali metal hydride making it necessary to avoid the presence of aluminum in the reactor when the desired product is alkali metal hydride and it is desired to use temperatures of from about 100° C to about 180° C in the first step of the reaction. Thus where aluminum is present in the reactor when the alkali metal and hydrogen are reacted to produce alkali metal hydride, a preferred temperature range of operation is from about 180° C to about 325° C, preferably from about 190° C to about 275° C, especially from about 200° C to about 225° C, typically 225° C.

When a two-step process is used to first produce alkali metal hydride and then secondly the alkali metal hydride thus formed is reacted with aluminum, trihydrocarbon aluminum and hydrogen to produce alkali metal aluminum dihydrocarbon dihydride, the two steps can be at the same temperature or at different temperatures, the same temperature ranges as set forth heretofore being applicable to both of the steps. In general, however, there is no need to maintain such temperature during any time interval between such steps. Thus the alkali metal hydride system from the first step can be cooled, stored, transported, etc. before being used in the latter step. Usually it is preferred to add the trihydrocarbon aluminum to the alkali metal hydride system when the two are at substantially room temperature and atmospheric pressure or only slightly elevated in regard to room temperature and atmospheric pressure.

In a preferred aspect of the present invention, the temperature is from about 190° C to about 275° C, the pressure is from about 500 to about 1250 pounds per square inch gage and the catalytic quantity of alkali metal aluminum dihydrocarbon dihydride is from about 10 to about 15 percent by weight based on the sodium fed to the process for reaction with hydrogen.

Preferably the temperature of the reaction of alkali metal and hydrogen in the presence of aluminum is about 225° C, the temperature at the addition of the trihydrocarbon aluminum is from about room temperature to about 225° C and the temperature at the reaction of alkali metal hydride, trihydrocarbon aluminum, aluminum and hydrogen is about 175° C.

Although the present process can be performed over the pressure range of from about 50 psig to about 5000 psig, generally the lower pressures are less desired because of low rates while the higher pressures are less desired because of equipment expense and are not really necessary for good reaction rate. Thus intermediate pressures of from about 100 psig to about 2000 psig are preferred with a narrower more preferred range being from about 250 psig to about 1750 psig, a still narrower range being from about 500 psig to about 1250 psig, with about 1000 psig being typical. These ranges apply in general where there is a reaction involving the addition of hydrogen to alkali metal or aluminum or mixed compounds or to such compounds containing other groups such as the R groups. Such hydrogen reaction is frequently termed a hydriding reaction. Thus these pressures are involved in the formation of alkali metal hydride according to the present process as well as to the conversion of alkali metal hydride into alkali metal aluminum dihydrocarbon dihydride. In general, suitable or desirable pressures are readily determind or optimized by one skilled in the art following the reaction procedures described herein in detail.

Reaction time is not critical. Normally, one uses a reaction time which is at least adequate to produce substantially complete reaction at the different stages, that is, for the production of alkali metal hydride as well as for the production of alkali metal aluminum dihydrocarbon dihydride. Normally, there is no need to prolong the reaction period and one prefers to use as short a reaction time as is possible to achieve the degree of conversion desired. Any longer reaction time represents a reduction in the production capability of a given autoclave; hence usually it is undesired. In general, useful reaction times range from about 0.01 to about 12 hours. Preferred reaction times range from about 1/2 hour to about 2 hours for each of the steps (1) producing the alkali metal hydride and of (2) producing the alkali metal aluminum dihydrocarbon dihydride from the alkali metal hydride.

The physical conditions used for the reaction are not critical except as indicated and have been disclosed herein to an extent which is ample to permit optimization in any respect by routine experimentation by one of ordinary skill in the art. The present examples illustrate the effect of various factors, seeking substantially complete reaction of the limiting reactant or reactants to the product of each respective stage.

Thus the aluminum and hydrogen are usually fed in excess above the stoichiometric amount required for the various reactions, the limiting reactant being the alkali metal in the case of the production of alkali metal hydride and either the alkali metal hydride or the trihydrocarbon aluminum in the case of the preparation of alkali metal aluminum dihydrocarbon dihydride from the alkali metal hydride. Normally, however, one prefers to use about stoichiometric proportions of three mols of alkali metal hydride and two mols of trihydrocarbon aluminum in the conversion of the alkali metal hydride to alkali metal aluminum dihydrocarbon dihydride.

For the examples, the reactor and all reactants fed are preferably placed in an anhydrous condition; however, residual moisture is readily removed where necessary by a preliminary contacting of the materials, for example, the toluene with alkali metal aluminum dihydrocarbon dihydride such as sodium aluminum diethyl dihydride or feeding the alkali metal last or bubbling the hydrogen through alkali metal aluminum dihydrocarbon dihydride. This material reacts readily but gently with water avoiding the violent reactions experienced where the water is contacted first with trihydrocarbon aluminum, alkali metal or alkali metal hydride.

From the foregoing and from the appended examples and claims, it is apparent to those skilled in the art that numerous arrangements can be made of the teachings, features and aspects of the present invention and that the invention is not to be limited except in accordance with the appended claims.

EXAMPLES I-IV

A 2-liter stainless steel Parr reactor equipped with external electric heater, internal cooling coils, baffles and twin-turbine air driven stirrer, thermometer, pressure gage and hydrogen feed system was used for Examples I-IV.

EXAMPLE I

The 2-liter reactor was charged with 800 ml of toluene, 81.5 grams of sodium and 8.15 grams of sodium aluminum diethyl dihydride, the latter in a 25 wt. percent solution in toluene. The system was purged with hydrogen and approximately 100 psig hydrogen pressure allowed to remain in the reactor as heating was begun. The stirrer was turned on when the temperature reached 125° C. (The melting point of sodium is 97.5° C.) When the temperature reached 220° C, the reactor was pressurized with hydrogen to about 1000 psig and the hydrogen supply valve closed. After two minutes, the pressure had dropped 160 psig and the reactor was again pressurized with hydrogen to about 1000 psig and the hydrogen supply again closed. After five minutes from the start of operation at 1000 psig, the pressure gage was again read. This time the pressure had dropped 140 psig. Again the reactor was quickly pressured to about 1000 psig following which a drop of 120 psig was observed at the 8 minute point. The procedure was continued with measurement and rapid repressurization to about 1000 psig at the 13, 20, 23, 28 and 41 minute points. The pressure drop results are tabulated hereinafter in the column, the consecutive pressure drops being added together in sequence to provide the Σ pressure drop figures which are those used in plotting Curve A of FIG. 1. Throughout the procedure the reactor temperature was held at about 220° C. The foregoing procedure is a simple way to determine reaction rate without requiring exact flow rate measurement for the pressurized hydrogen.

    ______________________________________                                         Time         Pressure (psig)                                                   (Minutes)    Δ        Ε                                          ______________________________________                                         0            --             --                                                 2            160            160                                                5            140            300                                                8            120            420                                                13           130            550                                                20            80            630                                                23            20            650                                                28           5              655                                                41           5              660                                                ______________________________________                                    

After the reaction, the vessel was cooled, the hydrogen pressure released and the dispersion of NaH in toluene discharged into a receiver. The dispersion was filtered to separate the sodium hydride from the toluene solution of sodium aluminum diethyl dihydride catalyst. The solid remaining was analyzed and shown to be NaH of purity higher than 95 percent.

EXAMPLE II

Example I was repeated at 225° C using 100 grams of sodium, 50 grams of powdered aluminum, 5 grams of sodium aluminum diethyl dihydride, and 500 ml of toluene.

    ______________________________________                                         Time         Pressure (psig)                                                   (Minutes)    Δ        Σ                                            ______________________________________                                         0            --             --                                                 3            100            100                                                9            150            250                                                15           140            390                                                21           130            520                                                30           120            640                                                41            60            700                                                57            20            720                                                ______________________________________                                    

The reaction rates of Examples I and II are comparable showing that the presence of the aluminum in Example II does not significantly affect reaction rate.

EXAMPLE III

Example I was repeated at 270° C but using 100 grams of sodium, 50 grams of aluminum powder, and 500 ml of toluene but without the NaAl(C₂ H₅)₂ H₂.

    ______________________________________                                         Time         Pressure (psig)                                                   (Minutes)    Δ        Σ                                            ______________________________________                                         0            --             --                                                 5            140            140                                                10           100            240                                                21           110            350                                                35            70            420                                                65            90            510                                                ______________________________________                                    

EXAMPLE IV

Example I was repeated at 225° C with 490 ml toluene and 106.5 grams of sodium, but without the NaAl(C₂ H₅)₂ H₂.

    ______________________________________                                         Time         Pressure (psig)                                                   (Minutes)    Δ        Σ                                            ______________________________________                                         0            --             --                                                 7            105            105                                                18            80            185                                                25            60            245                                                37           100            345                                                52           100            445                                                73           105            550                                                102          110            660                                                182           30            690                                                ______________________________________                                    

The preceding examples show a significantly higher reaction rate when the reaction is conducted in the presence of catalyst as specified and indicate that the presence of the aluminum powder does not significantly affect the reaction rate. Thus where the sodium hydride is subsequently reacted with triethyl aluminum and hydrogen to produce sodium aluminum diethyl dihydride, the aluminum powder needed for the latter reaction is suitably and conveniently added to the reactor prior to the formation of the sodium hydride.

EXAMPLES V-VII

These examples were conducted in a 5-gallon stainless steel pressure vessel, jacketed for heating externally. The vessel was equipped with pressure gage, thermometer, a hydrogen feed system, internal cooling coil for temperature maintenance and rapid cooling after the reaction. The reactor was baffled and equipped with an electrically driven twin turbine stirrer. Pressuring with hydrogen was periodic to 1000 psig as in Examples I-IV.

EXAMPLE V

The 5-gallon reactor was charged with 5800 grams toluene, 270 grams aluminum powder, 644 grams sodium, and 340 grams of 25 percent solution of sodium aluminum diethyl dihydride in toluene. (85 grams of contained NaAlEt₂ H₂, 13.2 percent on the sodium fed for the reaction with hydrogen). The reactor was purged with hydrogen, leaving 100 psig residual hydrogen pressure. The heater was turned on and the stirrer started when the temperature reached 150° C. Reactor heating was continued until a temperature of 220° C was reached, which temperature was subsequently maintained during the course of the reaction. Hydrogen was then fed for a 43 minute total reaction time.

    ______________________________________                                         Time         Pressure (psig)                                                   (Minutes)    Δ        Σ                                            ______________________________________                                         0            --             --                                                 4            160            160                                                10           170            330                                                16           130            460                                                27            70            530                                                36            30            560                                                43            10            570                                                ______________________________________                                    

The reactor was then cooled to 50° C, hydrogen pressure vented off and 2240 grams of liquid triethyl aluminum pressured into the reactor from a cylinder of triethyl aluminum.

The reactor was then heated to 170° C under hydrogen and then hydrogen was fed for a reaction time of 52 minutes at 170° C. Pressuring with hydrogen was periodic to 1000 psig as in the preceding sodium hydride preparation.

    ______________________________________                                         Time         Pressure (psig)                                                   (Minutes)    Δ        Σ                                            ______________________________________                                         0            --             --                                                 1            160            160                                                4            140            300                                                13           140            440                                                22            90            530                                                33            90            620                                                44           100            720                                                52            80            800                                                ______________________________________                                    

The reactor was again cooled to 50° C and hydrogen pressure vented off. 300 grams of tetrahydrofuran and 2125 grams of toluene was then pressured into the reactor. The reactor was then discharged and the product solution filtered yielding 11425 grams of solution. The solution was analyzed and found to contain 26.8 wt. percent NaAlEt₂ H₂ in a yield of 98 percent based on sodium, 100 percent based on triethyl aluminum.

EXAMPLE VI

Example V was repeated feeding 5950 grams of toluene, 300 grams of aluminum powder, 675 grams of sodium, and 240 grams of the 25 percent toluene solution of sodium aluminum diethyl dihydride. (60 grams of contained sodium aluminum diethyl dihydride, 8.9 percent on the sodium fed for the reaction with hydrogen). The time for the first reaction was 42 minutes.

    ______________________________________                                         Time         Pressure (psig)                                                   (Minutes)    Δ        Σ                                            ______________________________________                                         0            --             --                                                 5            130            130                                                9            130            260                                                12           120            380                                                18           110            490                                                27            40            530                                                42            30            560                                                ______________________________________                                    

The amount of triethyl aluminum fed was 2330 grams. The time for the subsequent or second reaction with hydrogen was 71 minutes.

    ______________________________________                                         Time         Pressure (psig)                                                   (Minutes)    Δ        Σ                                            ______________________________________                                         0            --             --                                                 1            140            140                                                3            110            250                                                8            150            400                                                15           120            520                                                23           90             610                                                36           60             670                                                50           80             750                                                65           60             810                                                71           10             820                                                ______________________________________                                    

EXAMPLE VII

A residual heel of several hundred milliliters retained from Example VI was used instead of feeding sodium aluminum diethyl dihydride. 670 grams of sodium, 300 grams of aluminum and 5000 grams of toluene were charged to the reactor. The reactor was heated to 220° C as in Example VI and then hydrogen fed for a 50 minute reaction at that temperature.

    ______________________________________                                         Time         Pressure (psig)                                                   (Minutes)    Δ        Σ                                            ______________________________________                                         0            --             --                                                 4            170            170                                                9            141            310                                                18           100            410                                                29            40            450                                                38            20            470                                                50            10            480                                                ______________________________________                                    

Data from the Examples are plotted as follows.

    ______________________________________                                          Example            Fig.                                                       ______________________________________                                         I                  1-A                                                         II                 1-B -III                                                    IV                 1-C                                                         V                  2-A                                                         VI                 2-A                                                         VII                2-B                                                         ______________________________________                                     

I claim:
 1. A process for producing alkali metal aluminum dihydrocarbon dihydride which comprises reacting alkali metal and hydrogen in the presence of an inert aromatic hydrocarbon solvent for the alkali metal aluminum dihydrocarbon dihydride and a catalytic amount of at least about 0.001 percent by weight of alkali metal aluminum dihydrocarbon dihydride, under conditions suitable to form alkali metal hydride, thereby producing alkali metal hydride, and then reacting the alkali metal hydride with trihydrocarbon aluminum, aluminum and hydrogen, in the presence of said solvent under conditions suitable to form alkali metal aluminum dihydrocarbon dihydride thereby producing alkali metal aluminum dihydrocarbon dihydride.
 2. The process of claim 1 wherein the alkali metal reacted is sodium, potassium or lithium.
 3. The process of claim 1 wherein the alkali metal reacted with hydrogen and the alkali metal of the alkali metal aluminum dihydrocarbon hydride are the same.
 4. The process of claim 1 wherein the alkali metal aluminum dihydrocarbon dihydride used is of the formula MAlR₂ H₂ wherein M is alkali metal and R is similar or different alkyl group having from about 2 to about 30 carbon atoms per alkyl group.
 5. The process of claim 4 wherein R is similar or different alkyl group having from about 2 to about 6 carbon atoms per alkyl group.
 6. The process of claim 4 wherein R is ethyl.
 7. The process of claim 1 wherein the alkali metal aluminum dihydrocarbon dihydride used is sodium aluminum diethyl dihydride.
 8. The process of claim 1 wherein the alkali metal aluminum dihydrocarbon dihydride used is sodium aluminum diisobutyl dihydride.
 9. The process of claim 1 wherein the catalytic quantity of alkali metal aluminum dihydrocarbon dihydride is from about 0.1 percent to about 50 percent by weight based on the alkali metal reactant fed to the process.
 10. The process of claim 1 wherein the catalytic quantity of alkali metal aluminum dihydrocarbon dihydride is from about 1 percent to about 20 percent by weight based on the alkali metal fed to the process.
 11. The process of claim 1 wherein the catalytic quantity of alkali metal aluminum dihydrocarbon dihydride is from about 10 to about 15 percent by weight based on the alkali metal fed to the process.
 12. The process of claim 2 wherein the solvent is toluene, xylene or benzene.
 13. The process of claim 2 wherein the trihydrocarbon aluminum compound is a trialkyl aluminum having from about 2 to about 30 carbon atoms per alkyl group.
 14. The process of claim 1 wherein the trihydrocarbon aluminum compound is a trialkyl aluminum having from about 2 to about 6 carbon atoms per alkyl group.
 15. The process of claim 1 wherein the trihydrocarbon aluminum compound is triethyl aluminum.
 16. The process of claim 1 wherein the trihydrocarbon aluminum compound is tri-isobutyl aluminum.
 17. The process of claim 1 for producing sodium aluminum dihydrocarbon dihydrides wherein sodium is reacted.
 18. The process of claim 1 for producing potassium aluminum dihydrocarbon dihydrides wherein potassium is reacted.
 19. The process of claim 1 for producing lithium aluminum dihydrocarbon dihydrides wherein lithium is reacted.
 20. The process of claim 1 wherein the solvent is toluene.
 21. The process of claim 1 wherein the solvent is xylene.
 22. The process of claim 1 wherein the solvent is benzene.
 23. The process of claim 1 wherein the temperature of the step of producing the alkali metal aluminum dihydrocarbon dihydride from the alkali metal hydride is from about 100° to about 325° C.
 24. The process of claim 1 wherein the temperature of the step of producing the alkali metal aluminum dihydrocarbon dihydride from the alkali metal hydride is from about 150° to about 275° C.
 25. The process of claim 1 wherein the temperature of the step of producing the alkali metal aluminum dihydrocarbon dihydride from the alkali metal hydride is from about 175° to about 225° C.
 26. The process of claim 1 wherein the pressure of the step of producing the alkali metal aluminum dihydrocarbon dihydride from the alkali metal hydride is from about 50 to about 5000 pounds per square inch gage.
 27. The process of claim 1 wherein the pressure of the step of producing the alkali metal aluminum dihydrocarbon dihydride from the alkali metal hydride is from about 100 to about 2000 pounds per square inch gage.
 28. The process of claim 1 for producing sodium aluminum diethyl dihydride wherein the trihydrocarbon aluminum compound is triethyl aluminum, where sodium is reacted, where the temperature is from about 190° C to about 275° C, wherein the pressure is from about 500 is about 1250 pounds per square inch gage and wherein the catalytic quantity of alkali metal aluminum dihydrocarbon dihydride is from about 10 to about 15 percent by weight based on the sodium fed to the process.
 29. The process of claim 1 wherein the alkali metal and hydrogen and reacted in the presence of an inert aromatic hydrocarbon solvent for the alkali metal aluminum dihydrocarbon dihydride and a catalytic amount of at least about 0.001 percent by weight of alkali metal aluminum dihydrocarbon dihydride based on the alkali metal fed to the process, in the substantial absence of free aluminum, at a temperature of from about 100° to about 325° C and at a pressure of from about 50 to about 5000 psig for a period of time of from about 0.01 to about 12 hours, thereby producing alkali metal hydride, and then the alkali metal hydride is reacted with aluminum, trihydrocarbon aluminum and hydrogen, in the presence of said solvent at a temperature of from about 100° to about 325° C and at a pressure of from about 50 to about 5000 psig for a period of time of from about 0.01 to about 12 hours, thereby producing alkali metal aluminum dihydrocarbon dihydride.
 30. The process of claim 1 wherein the alkali metal and hydrogen are reacted in the presence of free aluminum at a temperature of from about 180° to about 325° C and at a pressure of from about 50 to about 5000 psig for a period of time of from about 0.01 to about 12 hours, thereby producing alkali metal hydride in admixture with free aluminum, and then the alkali metal hydride and the aluminum are reacted with trihydrocarbon aluminum and hydrogen at a temperature of from about 100 to about 325° C and at a pressure of from about 50 to about 5000 psig for a period of time of from about 0.01 to about 12 hours, thereby producing alkali metal aluminum dihydrocarbon dihydride.
 31. The process of claim 30 wherein the catalytic quantity of alkali metal aluminum dihydrocarbon dihydride is from about 0.1 percent to about 50 percent by weight based on the alkali metal fed to the process.
 32. The process of claim 30 wherein the catalytic quantity of alkali metal aluminum dihydrocarbon dihydride is from about 1 percent to about 20 percent by weight based on the alkali metal fed to the process.
 33. The process of claim 30 wherein the catalytic quantity of alkali metal aluminum dihydrocarbon dihydride is from about 10 to about 15 percent by weight on the alkali metal fed to the process.
 34. The process of claim 30 for producing sodium aluminum diethyl dihydride wherein the trihydrocarbon aluminum compound is triethyl aluminum, where sodium is reacted, where the temperature is from about 190° C to about 275° C, wherein the pressure is from about 500 to about 1250 pounds per square inch gage and wherein the catalytic quantity of alkali metal aluminum dihydrocarbon dihydride is from about 10 to about 15 percent by weight based on the sodium fed to the process.
 35. The process of claim 30 wherein the amount of aluminum fed ranges from about stoichiometric to about 50 percent excess above stoichiometric based on the alkali metal and trihydrocarbon aluminum fed to the reaction.
 36. The process of claim 30 wherein the pressure of the step of producing the alkali metal hydride is from about 100 to about 2000 pounds per square inch gage.
 37. The process of claim 30 wherein the pressure of the step of producing the alkali metal hydride is from about 500 to about 1250 pounds per square inch gage.
 38. The process of claim 30 wherein the temperature of the step of producing the alkali metal hydride is from about 190° to about 275° C.
 39. The process of claim 30 wherein the temperature of the step of producing the alkali metal hydride is from about 200 to about 225.C.
 40. The process of claim 30 wherein the temperature of the step of producing the alkali metal hydride is about 225° C. 